Cellular interaction between B and T lymphocytes: enhanced release of B cell growth factor.

The release of a B cell growth factor (BCGF) in medium conditioned by peripheral blood T lymphocytes was shown to be dependent upon accessory cell derived signal(s). T lymphocytes activated with lectin and cultured in the presence of monocytes, or Interleukin 1, provided the in vitro components that were both necessary and sufficient for factor release. B, lymphocytes in the presence of both activated T cells and monocytes, were shown to further augment the amount of factor released by the T cell. The effects of the monocyte and B lymphocyte were, in part, mediated through the DR locus and these effects were consistent with a positive feedback mechanism for the regulation of the availability of BCGF. The data are discussed in terms of differing accessory cell roles for the monocyte and B cell in terms of the mechanisms underlying their augmentative effects on factor release.